Vanilla : Quite liked the way quests and zones were done (was I the only one?)

Nope. Not the only one. I actually enjoyed those quests MUCH more than the shit that happened to the old world when Cataclysm happened. And I really really wish that there could be a switch that lets you choose between classic and cata 1-60. I would choose classic every time.

You shouldn't count those things into a $40 product. That's what Blizzard wants you to do :x It gives things extra value they don't deserve, and devalues the $15 a month you pay.

You're missing the point. Those things you mentioned (transmog, etc) were included during a specific expansion, so they are counted as part of that expansion. The fact that the functionality extends beyond that expansion doesn't somehow invalidate that fact.

TBC: Flying Mounts
WOTLK :The way Arthas was mixed in the questing experience
CATA: That it entertained me long enough to play until Blizzcon and get the year subscription so i could play MoP Beta that was a real convincer for me to join WoW on the live servers again (in other words...i hated cata)
MoP:The look and feel of Pandaria

World pvp was poorly done in TBC, attempted but poorly done. There was a lot of downtime in TBC the first week, moreso then wotlk/cat/mop. Daily quests were introduced, tons of people would consider that a step backwards. A whole patch was basically dedicated to in-game voice communication. What a waste of development effort and time, did anyone ever use it? Is it even still in the game? I honestly don't know. Jumping in and out of portals for 45 minutes just to spawn an instance and 30+ minute 2v2 queue times later in the expansion we're not fun and actually drove a few of my friends to quit who have never come back to the game.

Yes it was arguably the most innovative and best expansion in wow's history but no not everything was awesome, lol.

Burning Crusade: Heroics and Karazhan
Wrath of the Lich King: Introduction of machinima cut scenes with Wrath Gate and proper use of phasing with Battle for Undercity
Cataclysm: Transmogrification
Mists of Pandaria: Too soon for me to decide what I'd name as my "good thing." So far I'm loving the expansion.

"There is good and evil in this world; we must find the black and white in the gray."

BC: Addition of Arenas. Made WoW feel competitive and made me strive to be a better player
Wrath: Ulduar best raid of all time no other raid did a better job of combining boss mechanics, story and graphics imo.
Cataclysm: RBGs were a good addition to the game. Not too many good things to say about Cata though lol
MoP: Questing was very impressive. In no other expansion do I think I was genuinely paying attention to what I was doing while questing.

TBC: Flying mounts, otherwise it is my least favorite of the expansions.
WOTLK: The environment (the zones were incredible and visually gorgeous, and to this day I can loop Grizzly Hills music and not get sick of it)
Cata: Streamlining 10s and 25s so they gave equal level loot. I always loved 40 mans from vanilla, but 25s were bleh. Evening the playing field for 10s meant I could play in a raid solely of close and real life friends.
MOP: Most enjoyable questing experience to date. Unlike in all of the other expansions, I actually had a great time leveling in Pandaria.

Nope. Not the only one. I actually enjoyed those quests MUCH more than the shit that happened to the old world when Cataclysm happened. And I really really wish that there could be a switch that lets you choose between classic and cata 1-60. I would choose classic every time.

I'd love to be able to quest through 1-60 vanilla-style. The new questing is just "meh".

Just one thing?
BC: Isle of Quel'Danas (pvp and pve-wise)
Wrath : Story (I wish Arthas won in end even if it means our end)
Cata: Single-play quests (sadly almost only good thing too...)
MoP: Account wide achievements

The beginning of wisdom is the statement 'I do not know.' The person who cannot make that statement is one who will never learn anything. And I have prided myself on my ability to learn
Thrallhttp://youtu.be/x3ejO7Nssj8 7:20+ "Alliance remaining super power", clearly blizz favor horde too much, that they made alliance the super power

TBC - The raiding taken to a new level, especially Kara, SSC, TK and SWP.
WotLK - Ulduar before the nerf hammer.
Cataclysm - Reforge and LFR.
MoP - So far I like the difficulty on the raids. It's not as easy as it has been in WoTLK and Cataclysm imo.

World pvp was poorly done in TBC, attempted but poorly done. There was a lot of downtime in TBC the first week, moreso then wotlk/cat/mop. Daily quests were introduced, tons of people would consider that a step backwards. A whole patch was basically dedicated to in-game voice communication. What a waste of development effort and time, did anyone ever use it? Is it even still in the game? I honestly don't know. Jumping in and out of portals for 45 minutes just to spawn an instance and 30+ minute 2v2 queue times later in the expansion we're not fun and actually drove a few of my friends to quit who have never come back to the game.

Yes it was arguably the most innovative and best expansion in wow's history but no not everything was awesome, lol.

Almost everything then, dailies do suck but I didn't mind back then cause I only had one toon and was very adamant I didn't want more, now that I have multiple 85+ toons I hate dailies more than anything even if it is easy money, the voicechat worked fine for small groups wich is all anyone every used it for so it's ok but sure not necessary at all, can't remember any downtime whatsoever but then again I had a completely diffrent schedule then and didn't play nearly as much as I do now so I probably was just lucky and missed it, mostly did 3v3 arenas and can't recall any overly long ques there so again lucky perhaps, and fighting over halaa was great I just loved that the others not so much but halaa was a highpoint for me.

That's just the things you commented on but if you want to make a list of the good things it would cover the entire page.

Honorable Mentions: Transmog, Farmville, Flying Mounts (though some could argue that it is detrimental to the game), Ulduar Lore, Pandaren, Worgen, and Goblin Glider (possibly the single coolest thing in the entire game!)